Eagonn's Tomb will have been marked on your map. Make your way there. Once inside, head up to the tomb and grab the Mystic Hammer (remains). You won't encounter any enemies here. With the remains in your hands, head to Ironfast Keep.

Gwyn Anwy will already be there. She says that the Mystic Hammer can only be reforged in the Hall of the Firstsworn, so head there. Inside, Gywn will say that you need to head through the Sacred Passage in order to get to the forge that can repair the Hammer.

Make your way through the Hall. Gwyn's mother's corpse can be found near the entrance of the Sacred Passage. Gwyn will attempt to open it but she is knocked back by an unseen force. You will have to open the door yourself. Inside there is a small scene where a voice tells you that the Hammer must be re-made. Head on to Vlaskar's Forge, further ahead. Use it, and the Mystic Hammer will be reforged and in your hands. Gwyn will now tell you that Anru Besin is at Cloudcrest Mountain, already trying to free the Niskaru Lord, Khamazandu inside it. She will head to Ironfast Keep for reinforcements. The quest ends here (XP and Gold, both level-based ~5800 and 15150 at level 31).

Head over to Cloudcrest Mountain when you wish to continue on to the next faction quest, The Mountain Prison.